Hydraulic elevator control system



Oct. 9, 1962 w. M. RUSSELL ET AL HYDRAULIC ELEVATOR CONTROL SYSTEM 5Shee Filed March 28, 1960 ts-Sheet 1 @ATcH s n'cu "/c U P LEVEL HATCHBWITCH Pusn BurroN 3 /5 /0 PUSH BUTTON DOWN *ifi DOWN LEVEL HATCH swn-cHQ r HATCH GVVJTCH INVENTORJ. r7, fiusstu.

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Oct. 9, 1962 w. M. RUSSELL ET AL 3,057,160

HYDRAULIC ELEVATOR CONTROL SYSTEM Filed March 28, 1960 3 Sheets-Sheet 24- 7, 1=1q. qr-

INV EN TORS. Mum N kusstLL, 9. 1? M4 LII/M AIIWAENCE,

Oct. 9, 1962 w. M. RUSSELL ETAL 3,

HYDRAULIC ELEVATOR CONTROL SYSTEM Filed March 28, 1960 5 Sheets-Sheet 30\ m g E Q x g s 3 N It: QQ.

INV EN TORS Uite tates atent $557,161) HYDRAULIC ELEVATUR CONTRQL SYSTEMWilliam M. Russell and Anthony P. W. Lawrence, Indianapolis, nd,,assignors to .l. l). Gould Company, Indianapolis, Ind., a copartnersliipFiled Mar. 28, 1960, Ser. No. 18,160 Claims. (Ci. 60-52) This inventionrelates generally to control systems for hydraulically-operated ram typeelevators, and particularly to a system for accomplishing two-speedleveling and stopping of the ram as it mOVes in the up direction.

In conventional practice several methods are utilized for up-leveling ahydraulic elevator. The more common of these requires raising theelevator car somewhat above the floor level at which it is to be stoppedand then lowering the car to the proper floor level by means of thedownward motion control valves. This system was used primarily becausepressure variations due to the various loads on the elevator car affectthe control accuracy much less in the downward movement of the car.

The system of the present invention provides a twoway up-levelingcontrol arrangement, that is, the system accomplishes an accurateleveling of the elevator car while moving only in the up directionindependently of the loading of the elevator car. The systemincorporates various valves and hydraulic connections so as to start theelevator car from rest in the up direction with a gradually acceleratedmotion until full up speed is reached. As the car reaches apredetermined point below the desired floor level, the car isdecelerated to a constant, predetermined leveling speed and is thenstopped at the floor level. The system maintains a constant level ingspeed as the elevator car approaches its stop position independently ofthe load on the elevator.

The fundamental component in the system is a multiple position flowrestricting means which meters the flow of hydraulic fluid to theelevator ram. Conventional practice utilizes one or more bypass valvesto divert a portion of the hydraulic fluid pump capacity from theelevator ram when the lower speed is desired. Since the flow ratethrough a given valve or restriction varies as the pressure drop acrossthe valve, varying loads on the elevator cause variation in the systempressure and, therefore, cause the conventional bypass valves to admit agreater amount of fluid at increased loads and a lesser amount of fluidat decreased loads. The system of the present invention maintains asubstantially constant pressure drop across the flow restricting meanswhich meters fluid to the ram and thus provides the elevator with aconstant speed regardless of the load on the elevator. The systemfurther includes means to start the elevator with gradual accelerationto full speed and to slow to levelling speed as required. The systemfurther includes means to bypass back to the hydraulic fluid reservoirthe full flow capacity of the pump so as to halt the elevator accuratelyat the desired floor level.

The control system utilizes a positive displacement hydraulic fluid pumpwhose suction side is connected to a hydraulic fluid reservoir. Thedischarge side of the pump is connected through a spring-loaded checkvalve to the elevator ram. The multi-position flow restricting means isinterposed in the hydraulic line between the pump and the check valve. Abypass valve is connected into a hydraulic line leading from the pumpdischarge side to the fluid reservoir. Initially when the pump isstarted the total flow is bypassed through the bypass valve to thereservoir. At an adjustably timed period thereafter the bypass valvecloses, starting gradually accelerated flow to the elevator ram and thecar moves upward at a uniform speed. At a predetermined point below thedesired floor level for the car the flow restrictice "3 A14 ing means ismoved to a position in which the flow to the elevator ram is throttledand the car is slowed to leveling speed. As the flow restricting meansthrottles flow to the ram, the bypass valve opens sufficiently tomaintain a predetermined pressure drop across the flow restricting meansand this pressure drop is maintained substantially constantindependently of the loading of the elevator car. The car is thusprovided with a constant speed in the leveling zone. At the desiredstopping point for the car the bypass valve is completely opened tobypass the full capacity of the pump to the reservoir, and the pumpdrive motor is simultaneously de-energized. Any coasting of the motor,pump and accompanying mechanical components is absorbed in pumping fluidto the reservoir and does not affect the accuracy of the elevator stop.

The primary object of the present invention is, therefore, to provide ahydraulic control system for a ram type hydraulic elevator or otherpositioning means in which a multi-position flow restricting means isutilized to meter flow to the elevator ram. To provide the desired ramspeed, the pressure drop across the flow restricting means, andconsequently the speed of the elevator is maintained substantiallyconstant independently of the loading of the elevator.

A further object of the present invention is. to provide a system of thetype referred to which includes means to start the elevator with gradualacceleration to full speed, to slow the elevator to leveling speed, andto stop the elevator at a given point accurately and constantly,regardless of car load or system pressure.

A further object of the present invention is to provide a bypass valveadapted to be utilized in the elevator control system, the valve havinga pressure responsive actuator for operation thereof, resilient meansbiasing the valve closure toward closed position, and pressureresponsive means for removing the bias of the resilient means for thevalve closure.

A further object of the present invention is to provide a bypass valveof the type referred to having means responsive to abnormally highpressure at the bypass valve inlet for passing fluid even though thevalve closure is in closed position.

A further object of the present invention is to provide a multi-positionflow restricting means operated by an electrically energized pilot valveand having adjustable means for timing the period between assumption ofits minimum flow position and the energization of its pilot operator.

The full nature of the invention will be understood from theaccompanying drawing and the following description and claims:

FIG. 1 is a schematic view of the hydraulic system of the presentinvention.

FIG. 2 is a side sectional view of the bypass valve component of thesystem.

FIG. 3 is a top plan view of the valve of FIG. 2.

FIG. 4 is a side sectional view of a solenoid operated pilot valveforming a component of the system of FIG. 1.

FIG. 5 is a side view of the multi-position flow restricting means orvalve which is a part of the system of FIG. 1.

FIG. 6 is a sectional view taken generally along the line 6-6 of FIG. 5.

FIG. 7 is a schematic wiring diagram of the electrical connections forthe system.

Referring initially to FIG. 1 the system includes a conventional,positive displacement pump 10 driven by an electric motor 11. Thesuction line 12 of the pump communicates through a filter 13 with ahydraulic fluid reservoir indicated generally at 14. A primary hydraulicline 16 joins the pump discharge line 17 with a con- 27 to the fluidreservoir.

9 ventional elevator-operating hydraulic ram indicated generally at 18.The line 1 6 has interposed therein a flow restricting means indicatedgenerally at 19, and, downstream thereof a check valve 21. A hydraulicline 22 connects the line 16 to the inlet passage 23- of a bypass valvegenerally indicated at 24. The outlet passage 26 of the valve 2 4communicates with the fluid reservoir by means of a line 27.

A line 28 connects the line 22 to a chamber within the valve 24 to besubsequently described. A line 29 provides communication between thisinternal chamber and the inlet side of a pilot valve 31. The outlet sideof the pilot valve 31 is connected by means of a line 32 to the fluidreservoir. A hydraulic line 33 provides communication between a furtherchamber within valve 24, to be subsequently described, and a point inthe primary line 16 between the flow restricting means 19 and the checkvalve 21.

One or more return lines 36 provide communication between the primaryline 16 and the fluid reservoir downstream of the check valve 21.Interposed in these re turn lines are control valves 37 which areutilized to control the downward movement of the elevator car. Controlof the downward motion of the elevator car is not the subject of thepresent invention and the valves 37 are therefore not disclosed hereinin detail. They may take the form of the valve disclosed and claimed inRussell Patent 2,926,882, issued March 1, 1960, and assigned to theassignee of the present invention.

Referring to FIGS. 2 and 3, the construction of the bypass valve 24 willnow be described in detail. The valve structure includes a valve body 38having the inlet passage 23 and the outlet passage 26. As will beevident from FIG. 1, the inlet passage communicates with the line 22 andthe outlet passage communicates with the line The passages are separatedby a bridge 39 having an aperture therein bounded by a valve seat 41.The upper end of the body is threaded to receive a bonnet nut 42 which,by means of a clamp ring 43 and sealing ring 44, supports a cylindricalelement 46 on the valve body. Reciprocable within the lower end of theelement 46 is a piston valve or closure member 47 whose lower end isconically shaped and cooperates with the valve seat 41. An O-ring 48provides a seal between the member '47 and the adjacent sides of theelement 46. The central bore within the element 46 is enlarged at itsupper end to provide a shoulder 49, the shoulder providing a downwardlimit for a piston 51 reciprocable within the enlarged upper portion ofthe bore. A sealing ring '52 carried by the piston 51 engages adjacentsides of the element 46. The piston 51 thus divides the central bore inthe element 46 into a twoway ram pressure chamber 53 and a pump pressurechamber 54. A central downwardly-extending portion 51a of the piston 51retains a helical compression, spring 56 which at its upper end bearsagainst the piston and at its lower end bears against the inset face 47aof the closure member 47.

The upper end of the element 46 has a cap or closure 57 which is rigidlysecured in place by means of lock screws as indicated at 58. A sealingring 59 seals off the upper end of the element 46. The cap 57 isprovided with a vertical passage 61 which communicates with the chamber54, the cap being threaded adjacent the upper end of the passage toaccommodate the needle valve assembly 62. The needle valve assembly isof conventional type and includes a lock nut 63, and a needle 64 havinga knurled head "66. The lower end of the needle cooperates with areduced-diameter portion of the passage 61 to provide an adjustablerestriction in the passage. The cap 57 is further provided with athreaded aperture which accommodates an adjustment screw 67 whichextends through the cap and into the chamber 54 and O-ring 68 seals theentry of the screw and a lock nut 69 clamps the screw in adjustedposition.

The central portion of the element 46 is provided with aradially-extending threaded aperture 71 which accommodates a fitting(not shown) for securing the line 33 (FIG. 1) thereto. The aperture 71thus provides for the introduction of ram pressure, that is, thepressure downstream of the flow restricting means 19, into the chamber53. The cap 57 is provided with a radially extending threaded aperture72 which receives a fitting (not shown) coupling the line 28 (FIG. 1) tothe passage 61. The aperture 72 thus introduces pump pressure into theupper portion of the passage 61. The fluid flow resulting from thispressure must pass the restriction provided by the needle 64 beforeentering the chamber 54. Any changes in pump pressure thus are reflectedin the chamber 54, but only after a time delay which is proportional tothe adjustment of the needle 64. As indicated in FIG. 3, the cap 57 isprovided with a further radially extending aperture 73 whichcommunicates with a vertical passage 74 formed in the cap andterminating at the chamber 54. The aperture 73 accommodates the line 29(FIG. 1), this hydraulic line extending to the inlet passage of thepilot valve 31 shown in detail in FIG. 4.

A high pressure relief valve structure is provided in the closure member47 and includes a piston 76 reciprocable within an axial aperture in theclosure member. The closure member aperture is connected with theannular extending passages 77 communicating with the central apertureand a conically-shaped valve member 78 closes the central apertureagainst the passages 77. The valve member 78 accommodates a portion ofthe reduced upwardly-extending end 76a of the piston 76 and its upperportion is four-sided to provide communication between the upper portionof the central aperture through the element 47 and the inclined passages77 when the piston moves the member 78 upwardly. A threaded adjustingmember 79 seats a compression spring 81 whose lower end bears againstthe member 78 and urges it downwardly into closed position. An axialpassage 82 in the member 79 provides communication to the chamber 53.Adjustment of the position of the member 79 with relation to the member47 thus varies the force exerted by the spring 81 and adjusts thepressure in the inlet passage 23 required to move the piston 76sufiiciently to unseat the member 78. Unseating of the member 78relieves the pressure in the chamber 53 and permits the now unbalancedpressure in the inlet passage 23 to move the member 47 upwardly tounload the pump.

Referring now to FIG. 4, the pilot valve 31 will be described in detail.The pilot valve 31 is of conventional type and includes an electricallyenergized coil 83 accommodated within a housing 84. The coil axiallyaccommodates a magnetic plunger 86 which is urged upwardly by a spring87. The plunger carries a valve closure member 88 whose lower endcooperates with the frustoconically shaped valve seat 89. The seat 89 isformed in a fitting 90 threaded into an element 91 which is apertured toprovide the outlet passage 92 for the valve. The element 91 is threadedinto a valve body element 93 which is apertured to provide the inletpassage 94 for the valve 31, this passage communicating with thehydraulic line 29. The pilot valve 31 is of the normally open type andwhen the coil 83 is de-energized fluid may flow freely between the inletpassage 94 and the outlet passage 92. When the valve is energized, theplunger 86 and closure member 88 are moved outwardly so that the closuremember shuts off the flow 'of fluid through the valve. The outletpassage 92 of the pilot valve communicates with the hydraulic line 32('FIG. 1) to the fluid reservoir.

The flow restricting means or metering valve 19 will now be describedwith reference to FIGS. 5 and 6. The valve includes a body portion 101having an inlet chamber 102 and an outlet chamber 103. The inlet chamberand outlet chamber are separated by a bridge 104 which is apertured toprovide a valve seat 106. Cooperating with the valve seat is a valveclosure 107 having a threaded portion received within a sleeve 109. Theupper end of the sleeve accommodates :an element 110 having an annularflange 111 which serves to clamp the piston 112 to the stem formed bythe sleeve 109 and the element 110. The piston is slidably receivedwithin the central bore of the upper tubular portion 113 of the valvebody 101, a seal being maintained between the piston and the bore bymeans of an O-ring 114. The element 110 is further provided with anannular flange 116 which supports one end of a compression spring 117,the upper end of the spring 117 engaging the base of a central,depressed portion of a bonnet or cap 118. The cap is threadedly receivedupon the upper end of the valve body portion 113, an O-ring maintaininga seal therebetween. A set screw 121, threaded through an aperture inthe valve body and engaging the lower margin of the cap 118, determinesthe depth to which the valve body portion 113 may enter the cap 118.

A central passage 122 extends through the element 110 and an alignedpassage 123 extends through the valve closure 107. Sidewardly extendingpassages 124 in the valve closure communicate with the passage 123. Thelowermost position of the valve closure is determined by a stem orabutment 126 which is threaded through and extends exteriorly of a plug127. The plug is received within a threaded aperture 128 at the base ofthe valve body 101. An O-ring 130 provides a seal between the stem andthe plug. A lock nut 131 threaded on the extending portion of the stemlocks the stem in adjusted position. The stem is provided with a centralpassage 129 which communicates with a sidewardly extending passage 132.As may be seen in FIG. 6, when the closure member 107 is in engagementwith the stem 126, the passage 123 is aligned with the passage 129.

Communication between the chamber 133, located above the piston 112, andthe passage 122 is prevented by a closure member 134 which engages thebeveled upper end of the element 110. The closure member has aconventional, lost-motion connection with a magnetically permeableplunger 136 which is recipro-cable within a non-permeable sleeve 137,the plunger being urged to its lowermost position within the sleeve bymeans of a compression spring 138. Mounted on the cap 118 and enclosingthe sleeve 137 is a solenoid coil 139. A conventional cap 141 andhousing body 142 enclose the solenoid. The arrangement of the solenoidcoil and the closure member 134 is such that when the coil isdeenergized, as shown in FIG. 6, the closure member blocks the upper endof the passage 122. When the coil 139 is energized, the closure member134 is lifted from the upper end of the passage 122 and communication isestablished with the chamber 133.

Extending through one side of the valve body 101 is a passage 143 whoseupper end communicates with the chamber 133 and whose lower end isbeveled to provide a throttling aperture 144 communicating with thevalve inlet chamber 102. Cooperating with the throttling aperure is aconventional needle valve assembly 146 which includes an adjustable,positionable stem 147. The stem cooperates with the throttling apertureto obstruct flow from the chamber 102, through the passage 143, and intothe chamber 133. On the opposite side of the valve housing there isprovided a similar passage 148 whose upper end communicates with thechamber 133 and whose lower end is closed by the tapered end of anadjustable stem 149, forming a part of a conventional needle valveassembly 151.

As will be evident from FIG. 6, with the inlet chamber 102 accommodatinghydraulic fluid under pressure and with the passage 122 blocked by theclosure member 134, the structure in the chamber 133 will be at the samepressure as the structure in the chamber 102, that is, the pressure onopposite sides of the piston 112 will be equal. Under these conditions,the spring 117 will hold the closure member 107 against the stem 126,that is, in its lowermost position, as shown in FIG. 6. Upon energize.-tion of the solenoid coil 139, the closure member 134 will be movedupwardly to open the pasage 122, relieving the pressure in the chamber133 above the piston. The piston will thereupon be moved upwardly untilit engages the inner, end face of the cap 118, thereby moving theclosure member 107 into its uppermost position. Upon subsequentde-energization of the coil 139, the closure member 134 will close thepassage 122 whereupon the pressure in the chamber 133, above the pistonwill rise to the pressure of the inlet chamber 102., permitting thespring 117 to return the closure member 107 to its lowermost position.The time interval between closure of the passage 122 by the member 134and the engage ment of the closure member 107 with the stem 126 isdetermined by the position of the stem 147 with relation to thethrottling aperture 144 of the passage 143. Adjusing the stem 147inwardly increases the time interval and adjusting it outwardly awayfrom the aperture 144 decreases the time interval.

The stem 149 provides a manual means for establishing communicationbetween the chamber 133 above the piston and the outlet chamber 103 andis intended for emergency use only, that is, under conditions wherein,for example, the solenoid coil 139 is disabled or its circuit broken sothat it cannot be energized.

The electrical interconnection between the system components will now bedescribed with reference to FIG. 7. Que side of the electrical source ofpower is connected by means of the input line 152 to one side of anormally open push button switch 153 physically located in the elevatorcar. The other side of the switch 153 is connected by means of a wire154 to one side of a normally closed, up-stop switch 155. The switch 155is cammed into open position as the elevator car reaches the proper stoplevel during its upward travel. The other side of the switch 155 isconnected by means of a wire 156 to the pump motor 11, the motor beingfurther connected by means of a wire 157 to an input line 158. A wire159 connects one side of the pilot valve coil 83 to the wire 156, theother side of the coil 33 being connected by means of a Wire 1611 to theinput line 158. The wire 154 is con nected by means of a wire 162 to oneside of a normally closed up-level switch 163.

The switch 163 is cammed to open position as the elevator car reachesthe leveling zone in its upward travel and prior to the opening ofswitch 155. The other side of the switch 163 is connected by means of awire 164 to one side of the solenoid coil 139 incorporated in the howrestricting valve 119. The other side of the coil 139 is connected bymeans of a wire 166 to the input line 153. The wire 152 is connected bymeans of a wire 167 to one side of a normally open, push button, downswitch 163 which is physically located in the elevator car. The otherside of the switch 168 is connected by means of a wire 169 to one sideof a normally closed, down-stop switch 171. The switch 171 is cammed toopen position as the elevator car reaches the desired stop level in itsdownward motion. The other side of the switch 171 is connected by meansof a wire 172 to one side of one of the operating coils for the controlvalves 37. The wire 169 is connected by means of a wire 173 to one sideof a normally closed, down-level switch 174. The switch 174 is cammed toopen position as the elevator car reaches the leveling zone in itsdownward travel and prior to the opening of the switch 171. The otherside of the switch 174 is connected by means of a wire 176 to thesolenoid operating coil of another of the control valves 37. All of thecontrol valves 37 are connected to the input line 158 by appropriatewiring.

As previously mentioned, since the downward leveling of the elevator caror ram is not a part of the present invention, the function of theswitches 168, 174 and 171 and the functioning of the control valves 37is not described in detail herein. It will be understood that FIG. 7

is a schematic illustration only, and the various control componentsmight be placed in a low voltage circuit and the pump might be providedwith three phase power and controlled through an appropriate relayarrangement. Further, it will be understood that the normally open pushbutton switch 153 is provided with suitable hold-in contacts so that theswitch push button need be only momentarily actuated to maintain itscontacts in closed condition, opening of the up-stop switch 155 servingto return the contacts of the switch 153 to open position.

Operation The operation and adjustment of the system, with primaryreference to FIGS. 1 and 7, will now be described. With the electricalcircuit in a quiescent state as indicated in FIG. 7, all of the solenoidoperating coils and t. e pump motor will be deenergized, the energizingcircuit being broken at the switch 153. Since the pilot valve operatorcoil 83 is deenergized this valve will be open and the pressure abovethe piston 51 of the bypass valve 24 will be relieved. The piston valve47 will therefore be in its upper position, that is, displaced away fromthe valve seat 41. Manual closure of the push button upswitch 153energizes the pilot valve coil 83 and also energizes a coil 139 which isincorporated in the flow restrictin valve 19 together with the motorpump 11. The pump pressure is thereupon developed by the pump. However,the full flow capacity of the pump is initially bypassed through theopen valve 24 to the fluid reservoir 14. Energization of solenoid coil83 closes pilot valve 31 and this closure causes the pressure in thechamber 54, acting upon the piston 51 in the valve 24, to build up. Therate of build-up of pressure in the chamber 54 is determined by the rateof admission of fluid through the line 28 into the chamber 54. This rateof fluid admission is dependent upon the adjustment of the needle 66forming a part of the needle valve assembly 62 (FIG. 2). The timedincrease of pressure in the chamber will cause the piston valve 47 tomove downwardly and approach its seat 41. As the piston valve 4 7approaches its seat, hydraulic fluid flow is diverted to the main line16 and, since the solenoid coil 139 of the flow restricting valve 19 isenergized, the piston 112 of the valve 19 will be moved to its uppermostposition, removing the valve closure 107 away from its seat 106.Hydraulic fluid is thereupon admitted through valve 19 from the inletchamber 102 to outlet chamber 193 to the check valve 21 and to the ram18, starting the upward movement of the ram. It will be noted that theelevator car does not attain full velocity until the bypass cycle of thevalve 24 is completed and the rate of acceleration of the car fromimmobility to full upward velocity is determined by the adjustment ofthe needle valve 62. It should be noted that the valve 19 meters theflow directly to the ram 18. The position of the cap 118 of the valve 19is adjusted with relation to the valve body portion 113 so as to fix theupper position of the valve closure 167 at a point where the valve 19will pass 100% of the pump capacity at an inlet to outlet pressuredifferential or pressure drop of the order of to p.s.i.g., this pressuredifferential being necessary to insure proper valve response.

As the elevator car travels upwardly it will eventually enter theup-leveling zone determined by the opening of the up-level switch 163.The opening of switch 163 deenergizes the solenoid coil 139 of the valve19, permitting the closure member 134 to move to its position of FIG. 6,closing the passage 122. This causes the pressure in the chamber 133above the piston 112 in the valve 19 to build up. Increase in pressurein the chamber 133, that is, the equalization of the pressure onopposite sides of the piston 112 causes the member M7 to move toward itsextreme lower position of FIG. 6. This downward motion of the valvemember 107 decreases the flow of fluid to the elevator ram and slows thecar to a leveling speed whose ultimate magnitude is determined by theadjusted position of the stem 126 which fixes the lowermost position ofthe member 167. The rate of deceleration from full up velocity toleveling zone velocity of the car is determined by the adjustment of theneedle 147 with relation to the aperture 144 in the passage 143. Thiswill be evident from FIG. 6, wherein it will be noted that the rate ofpressure build-up in the chamber 133, above the piston 112, upon closureof the passage 122 is determined by the degree of obstruction of thepassage 143.

As the valve member 107 of the valve 19 approaches its lowermostposition, as described above, the pressure in the line 22 (FIG. 1)communicating with the valve 24 begins to rise, that is, the pressuredilferential across the valve 19 tends to rise. Since the piston valveclosure 47 in the bypass valve 24 is held in closed position by rampressure (introduced into the chamber 53 by means of the line 3 3 andthe aperture 71) plus the force exerted by the spring 56, as thepressure in the line 22 rises the piston valve member 4-7 will be liftedofi its seat so as to bypass through the line 27 to the fluid reservoirsuflicient fluid to maintain the pressure drop across the valve 19 atsubstantially the same value as the pressure drop thereacross prior tomovement of the member 107 in the valve 19 to its lowermost position. Itshould be noted that during the upward motion of the piston valve member47 the piston 51 remains in its position of FIG. 2 and the relativemotion of the valve member 47 with respect to the piston 51 isaccommodated by fiexure of the spring 56. Because of the reduced flow tothe ram, the elevator car proceeds through the leveling zone at areduced speed. As the car reaches the desired stop-level, the switch iscammed open, breaking the circuit to the pump motor and to the pilotvalve operating coil 83. The consequent opening of the pilot valve 31relieves the pressure in the chamber 54 above the piston 51 in thebypass valve 2 thereby permitting the piston valve member 47 to move toits furthermost open position. This opening of the bypass through thevalve 24 to the fluid reservoir simultaneously with shutting down thepump motor permits any coasting of the pump and associated mechanicalparts to merely pump fluid to the reservoir rather than increasing theflow in the line 16.

As previously mentioned, the needle valve 62 in the bypass valve 24determines the magnitude of the acceleration of the elevator car fromimmobility to full-up velocity. The adjusting screw or stem 67determines the pilot pressure or minimum pressure. It is preferablyadjusted so that it establishes a maximum open position for the bypassvalve 24 such that with the elevator car empty and with the pumpoperating, the elevator car will remain immobile. In the event of anabnormal rise in pressure at the pump discharge line, the piston 76 willbe moved upwardly to relieve the pressure in the chamber 53 and therebypermit the unbalanced pressure in the inlet chamber 23 of the valve 24to move the member 47 upwardly to unload the pump. It will be noted thatthe system of the present invention provides a two-position orifice orflow restriction which meters hydraulic fluid flow directly to the ram.The change in flow of the fluid to the ram and the resulting increase inpressure upstream of the flow restricting or metering valve 19 iscompensated by the bypass valve 24 in such fashion as to maintain thepressure drop across the valve 19 at substantially the same valueindependently of whether the valve 19 is in its minimum flow or maximumflow position. The arrangement is such that the fluid flow to the ram isvaried directly to provide variations in car speed. 511106 the pilotvalve 31 is open when de-energized, immediately upon the loss ofelectrical power to the pilot valve, whether from power failure or fromswitch actuation, the pilot valve will be opened to permit the bypassvalve 24 to relieve the pump. It will be understood that as to thefunctioning of the system the various components such as the pilot valve31, bypass valve 24 and flow metering valve 19, might be separated intoseparate components or might all be collected in a single compositehousing. The scope of the present invention is intended to include anysuch obvious variations.

While the invention has been disclosed and described in some detail inthe drawings and foregoing description, they are to he considered asillustrative and not restrictive in character, as modifications mayreadily suggest themselves to persons skilled in this art and within thebroad scope of the invention, reference being had to the appendedclaims.

The invention claimed is:

l. A hydraulic control system for positioning the movable element of afluid motor to operate a ram-type hydraulic elevator or the likecomprising a source of hydraulic fluid 14 and a positive displacementpump having its suction side communicating with said source, a primaryhydraulic line 16 providing communication between the discharge side ofsaid pump and said fluid motor l8, flow restricting means 19 interposedin said primary line for metering fluid flow to said fluid motor, saidflow restricting means including a throttling memher 107 movable betweena first position providing maximum fluid flow and a second positionproviding minimum fluid flow, electrically energizable means 139operable so as to permit movement of said member to maximum flowposition when energized and to minimum flow position when deenergized, aby-pass valve 24 having its inlet side in communication with saidprimary line at a point upstream from said flow restricting means andhaving its outlet side communicating with said fluid source, said bypassvalve including a closure member 47 movable to control fluid flowbetween the inlet and outlet sides of said valve, said by-pass valvefurther including means providing a first chamber 54 and a secondchamber 53 separated by a first movable wall 51, a second movable wall47a for said second chamber, said closure member being rigidly connectedto and movable with said second movable Wall, resilient means 56extending between said first and second movable walls for exerting abiasing force tending to move said closure member to shut oflf flowbetween the inlet and outlet sides of said by-pass valve, means '33providing fluid communication between said second chamber and thedownstream side of said flow restricting means, means 28 providing fluidcommunication between said first chamber and the upstream side of saidflow restricting means, and electrically energizable valve means 31 forrelieving said first chamber, said last mentioned means comprising anormally open -valve providing fluid communication between said firstchamber and said fluid source, whereby with said electricallyenergizable valve means deenergized, the system is in a quiescent statewith said by-pass valve returning substantially all of the capacity ofsaid pump back to said source, subsequent energization of saidelectrically energizable valve means and said electrically energizablemeans causing said by-pass valve closure member to move to reduce fluidflow through said by-pass valve thus providing fluid flow to said fluidmotor as determined by a predetermined pressure drop across said flowrestricting means in maximum flow position, subsequent deenergization ofsaid electrically energizable means moving said throttling member tosaid minimum flow position, the consequent rise in pressure upstream ofsaid flow restricting means causing said by-pass valve closure member tomove toward open position to thereby substantially maintain saidpredetermined pressure drop across said flow restricting means withreduced fluid flow to said fluid motor.

2. A hydraulic control system as claimed in claim 1 having means foradjustably restricting fluid flow through said means providing fluidcommunication between said first chamber and the upstream side of saidflow restricting means whereby adjustment can be accomplished of therate at which fluid flow through said by-pass valve is reduced uponenergization of said electrically energizable valve means and saidelectrically energizable means.

3. A hydraulic control system for positioning the movable element of afluid motor to operate a ram-type hydraulic elevator or the likecomprising a source of hydraulic fluid and a positive displacement pumphaving its suction side communicating with said source, a primaryhydraulic line providing communication between the discharge side ofsaid pump and said fluid motor, flow restricting means interposed insaid primary line for metering fluid flow to said fluid motor, said flowrestricting means including a throttling member movable between a firstposition providing maximum fluid flow and a second position providingminimum fluid flow, electrically energizable means operable so as topermit movement of said member to maximum flow position when energizedand to minimum flow position when deenergized, a bypass valve having itsinlet side in communication with said primary line at a point upstreamfrom said flow restricting means and having its outlet sidecommunicating with said fluid source, said by-pass valve including aclosure member movable to control fluid flow between the inlet andoutlet sides of said valve, said by-pass valve further includingpressure responsive means for moving said closure member, meansproviding fluid communication between said pressure responsive means andboth the upstream and downstream side of said flow restricting means,and electrically energizable valve means for relieving said pressureresponsive means, said last men tioned means comprising a normally openvalve providing fluid communication between said pressure responsivemeans and said fluid source, whereby with said electrically energizablevalve means deenergized the system is in a quiescent state with saidbypass valve returning substantially all of the capacity of said pumpback to said source, subsequent energization of said electricallyenergizable valve means and said electrically energizable means causingsaid by-pass valve closure member to move to reduce fluid flow throughsaid by-pass valve thu providing fluid flow to said fluid motor asdetermined by a predetermined pressure drop across said flow restrictingmeans in maximum flow position, subsequent deenergization of saidelectrically energizable means moving said throttling member to saidminimum flow position, the consequent rise in pressure upstream of saidflow restricting means causing said by-pass valve closure member to movetoward open position to thereby substantially maintain saidpredetermined pressure drop across said flow restricting means withreduced fluid flow to said fluid motor.

4. A system for controlling the flow of hydraulic fluid to ahydraulically positioned device subjected to loads of various magnitude,comprising a source of hydraulic fluid and a positive displacement pumphaving its suction side communicating with said source, a hydraulic lineproviding communication between the discharge side of said pump and saidpositioned device, two-position flow restricting means having a flowcontrolling member movable between maximum flow and minimum flowpositions interposed in said line, said flow restricting means having apredetermined pressure drop thereacross when in its maximum flowposition, said flow controlling member being movable to its said minimumflow position in response to application of the pressure in said linethereto, first timing means for timing the application of line pressureto said flow control member, and means including a by-pass line forby-passing a portion of the capacity of said pump back to said fluidsource when said flow controlling member is in said minimum flowposition to thereby substantially maintain said predetermined pressuredrop across said flow restricting means whereby the fluid flow to saidpositioned device is independent of the loading thereof, said lastmentioned means further including a pressure responsive valve memberresponsive to pressure in said line and movable in response to suchpressure to obstruct flow through said by-pass line, and second timingmeans for timing the application of line pressure to said pres- 1 1 sureresponsive member, whereby the acceleration of said hydraulicallypositioned device may be varied by said second timing means and thedeacceleration thereof may be varied by said first timing means.

5. A system for controlling the flow of hydraulic fluid to ahydraulically positioned device subjected to loads of various magnitude,comprising a source of hydraulic fluid and a pump having its suctionside communicating with said source, a hydraulic line providingcommunication between the discharge side of said pump and saidpositioned device, two-position flow restricting means having a flowcontrol member movable between maximum flow and minimum flow positionsinterposed in said line, said flow restricting means having apredetermined pressure drop thereacross when said flow controllingmember is in its maximum flow position, said flow controlling memberbeing movable to its said minimum position in response to application ofthe pressure in said line thereto, first adjustable means for timing theapplication of line pressure to said flow control member, and means forbypassing a portion of the capacity of said pump back to said fluidsource when said flow controlling member is in said minimum flowposition to thereby substantially maintain said predetermined pressuredrop across said flow restricting means whereby the flow to saidpositioned device is independent of the loading thereof, said lastmentioned means further including a pressure responsive valve memberresponsive to pressure in said line and movable in response to suchpressure to obstruct flow through said by-pass line, and secondadjustable means for timing the application of line pressure to saidpressure responsive valve member, whereby the acceleration of saidhydraulically positioned device maybe varied by said second adjustablemeans and the deacceleration thereof may be varied by said firstadjustable means.

6. A hydraulic control system for positioning the movable element of afluid motor to operate a ram-type hydraulic elevator or the likecomprising pressure means supplying hydraulic fluid under pressure, aprimary hydraulic line providing communication between said pressuremeans and said fluid motor, flow restricting means interposed in saidprimary line for metering fluid flow to said fluid motor, said flowrestricting means including a throttling member movable between a firstposition providing maximum fluid flow and a second position providingminimum fluid flow, electrically energizable means operable to move saidmember to maximum flow position when energized and to minimum flowposition when deenergized, a by-pass valve having its inlet side incommunication with said primary line at a point upstream from said flowrestricting means and having its outlet side communicating with saidpressure means, said bypass valve including a closure member movable tocontrol fluid flow between the inlet and outlet sides of said valve,said by-pass valve further including means providing a first chamber anda second chamber separated by a first movable wall, a second movablewall for said second chamber, said closure member being rigidlyconnected to and movable with said second movable wall, resilient meansextending between said first and second movable walls for exerting abiasing force tending to move said closure member to shut off flowbetween the inlet and outlet sides of said bypass valve, means providingfluid communication between said second chamber and the downstream sideof said flow restricting means, means providing fluid communicationbetween said first chamber and the upstream side of said flowrestricting means, and electrically energizable valve means forrelieving said first chamber, said last mentioned means comprising anormally open valve providing fluid communication between said firstchamber and said fluid source, whereby with said electricallyenergizable valve means deenergized the system is in a quiescent statewith said by-pass valve dumping substantially all of the fluid flow fromsaid pressure means, subsequent energization of said electricallyenergizable valve means and said electrically energizable means causingsaid bypass valve closure member to move to reduce fluid flow throughsaid bypass valve thus providing fluid flow to said fluid motor asdetermined by a predetermined pres-. sure drop across said flowrestricting means in maximum flow position, subsequent deenergization ofsaid electrically energizable means moving said throttling member tosaid minimum flow position, the consequent rise in pressure upstream ofsaid flow restricting means causing said by-pass valve closure memtberto move toward open position to thereby substantially maintain saidpredetermined pressure drop across said flow restricting means withreduced fluid flow to said fluid motor.

7. A hydraulic control system as claimed in claim 2 having means foradjustably restricting fluid flow through said means providing fluidcommunication between said first chamber and the upstream side of saidflow restricting means whereby adjustment can be accomplished of therate at which fluid flow through said by-pass valve is reduced uponenergization of said electrically energizable valve means and saidelectrically energizable means.

8. A hydraulic control system for positioning the movable element of afluid motor to operate a ram-type elevator or the like comprising asource of hydraulic fluid and pumping means having its suction sidecommunicating with said source, a primary hydraulic line providingcommunication between the discharge side of said pumping means and saidfluid motor, flow restricting means interposed in said primary line formetering fluid flow to said fluid motor, said flow restricting meansincluding a throttling member movable between a first position providingfluid flow of a predetermined magnitude and a second position providingfluid flow of a lesser magni tude, actuating means operable to move saidmember to said first position when energized and to said second positionwhen deenergized, a by-pass valve having its inlet side in communicationwith said primary line at a point upstream from said flow restrictingmeans and having its outlet side communicating with said fluid source,said bypass valve including a closure member movable to control fluidflow between the inlet and outlet sides of said valve, said by-passvalve further including pressure responsive means for moving saidclosure member, means providing fluid communication between saidpressure responsive means and both the upstream and downstream side ofsaid flow restricting means, and valve means for relieving said pressureresponsive means by providing fluid communication between said pressureresponsive means and said fluid source, whereby with said valve meanspassing fluid the system is in a quiescent state with said by-pass valvereturning substantially all of the capacity of said pumping means backto said source, subsequent blocking of fluid flow by said valve meansand operation of said actuating means causing said bypass valve closuremember to move to reduce fluid flow through said by-pass valve thusproviding fluid flow to said fluid motor as determined by apredetermined pressure drop across said flow restricting means in saidfirst position, further operation of said actuating means moving saidthrottling member to said second flow position, the consequent rise inpressure upstream of said flow restricting means causing said by-passvalve closure member to move toward open position to therebysubstantially maintain said predetermined pressure drop across said flowrestricting means with reduced fluid flow to said fluid motor.

9. A system for controlling the flow of hydraulic fluid to ahydraulically positioned device subjected to loads of various magnitude,comprising a source of hydraulic fluid and pumping means having itssuction side communicating with said source, a hydraulic line providingcommunication between the discharge side of said pumping means and saidpositioned device, a multi-position flow restricting means interposed insaid line and having a flow control member movable between a firstposition permitting flow of a predetermined magnitude and at least onefurther position permitting flow of a lesser magnitude, said flowrestricting means having a predetermined pressure drop thereacross whensaid flow control member is in its first position, said flow controllingmember being movable to its said further position in response toapplication of the pressure in said line thereto, first adjustable meansfor timing the application of line pressure to said flow control member,and means for bypassing a portion of the capacity of said pump back tosaid fluid source when said flow controlling member is in its saidfurther position to thereby substantially maintain said predeterminedpressure drop across said flow restricting means whereby the fluid flowto said positioned device is independent of the loading thereof, saidlast mentioned means further including a pressure responsive valvemember responsive to pressure in said line and movable in response tosuch pressure to obstruct flow through said by-pass line, and secondadjustable means for timing the application of line pressure to saidpressure responsive valve member, whereby the acceleration of saidhydraulically positioned device may be varied by said second adjustablemeans and the deacceleration thereof may be varied by said firstadjustable means.

10. A hydraulic control system for positioning the movable element of afluid motor to operate a ram-type hydraulic elevator or the likecomprising a source of hydraulic fluid and a positive displacement pumphaving its suction side communicating with said source, a primaryhydraulic line providing communication between the discharge side ofsaid pump and said fluid motor, flow restricting means interposed insaid primary line for metering fluid flow to said fluid motor, said flowrestricting means including a throttling member movable between a firstposition providing maximum fluid flow and a second position providingminimum fluid flow, electrically energizable means operable so as topermit movement of said member to maximum flow position when saidelectrically energizable means is actuated in one sense and to minimumflow position when actuated in the opposite sense, a by-pass valvehaving its inlet side in communication with said primary line at a pointupstream from said flow restricting means and having its outlet sidecommunicating with said fluid source, said by-pass valve including aclosure member movable to control fluid flow between the inlet andoutlet sides of said valve, said by-pass valve further includingpressure responsive means for moving said closure member, meansproviding fluid communication between said pressure responsive means andboth the upstream and downstream side of said flow restricting means,and electrically energizable valve means for relieving said pressureresponsive means, said last mentioned means comprising a valve providingfluid communication between said pressure responsive means and saidfluid source, whereby with said electrically energizable valve meansactuated in one sense the system is in a quiescent state with saidbypass valve returning substantially all of the capacity of said pumpback to said source, subsequent actuation of said electricallyenergizable valve means in the opposite sense and said electricallyenergizable means in its said one sense causing said by-pass valveclosure member to move to reduce fluid flow through said by-pass valvethus providing fluid flow to said fluid motor as determined by apredetermined pressure drop across said flow restricting means inmaximum flow position, subsequent actuation of said electricallyenergizable means in its said opposite sense moving said throttlingmember to said minimum flow position, the consequent rise in pressureupstream of said flow restricting means causing said by-pass valveclosure member to move toward open position to thereby substantiallymaintain said predetermined pressure drop across said flow restrictingmeans with reduced fluid flow to said fluid motor.

References Cited in the file of this patent UNITED STATES PATENTS2,102,865 Vickers Dec. 21, 1937 2,331,026 Harrington Oct. 5, 19432,694,544 Hall Nov. 16, 1954 2,815,921 Bigelow Dec. 10, 1957 2,894,525Erickson July 14, 1959 2,905,190 Oyster Sept. 22, 1959

